The present invention relates to a dielectric resonator for microwave or VHF-UHF band, applicable especially for a microwave filter or an oscillator.
In the conventional microwave filter or oscillator, resonators of TEM mode are very popular. Such resonators are formed by strip line structures, such as an open ended resonant line 1 having a length equal to a half wave length as shown in FIG. 1A, an open ended U-shaped resonant line 2 having a length equal to a half wave-length as shown in FIG. 1B, a ring resonant line 3 having a length equal to a wave-length as shown in FIG. 1C, and a circular resonant line 4 having a gap 6 in which a capacitor 5 is provided to connect both ends of the resonant line 4 for shortening the length of the resonant line 4 to less than a half wave-length as shown in FIG. 1D. These strip line resonators are manufactured on dielectric plates by printing or photoetching techniques. Therefore, these structures may be suitable for mass-production and excellently exhibit uniform performance or characteristics.
However, it is necessary to make the resonator itself large in size, when a large unloaded Q (quality factor) is desired for reducing loss of the resonator. To make the resonator large in size, a thick dielectric plate must be used. This results large in size and expensive in cost.